1. Field of the Invention
The invention relates to memory devices and more particularly to phase change memory devices and methods for fabricating the same.
2. Description of the Related Art
Phase change memory devices are non-volatile, highly readable, highly programmable, and require low driving voltage/current. Current trends in phase change memory development are to increase cell density and reduce current density.
Phase change material in a phase change memory device has at least two solid phases, a crystalline state and an amorphous state. Transformation between these two phases can be achieved by changing the temperature of the phase change material. The phase change material exhibits different electrical characteristics depending on its state. For example, in its amorphous state the material exhibits a higher resistivity than in the crystalline state. Such phase change material may switch between numerous electrically detectable conditions of varying resistivities on a nanosecond time scale with the input of pico joules of energy. Since phase change material allows for a reversible phase transformation, memory bit status can be distinguished by determining the phase of phase change material in the memory bit.
For enhancing applications of phase change memory devices, size reduction of the memory cells in a phase change memory device is needed to increase cell density of the phase change memory device. With size reduction of the memory cells, however, pitches between adjacent memory cells are also reduced and may thus increases thermal disturbing or thermal cross-talk between adjacent memory cells of the phase change memory device. Therefore, undesired disturbing and/or bit-writing errors may occur to memory cells of the phase change memory device during operation.